Flow-Induced Nanopore Expansion: Insights from Molecular Dynamics Simulations

Nanoscale fluid dynamics is critical for extensive applications in seawater desalination, energy storage, and geo-energy extraction, especially in shale oil extraction. However, the relationship between fluid flow, nanopore deformation, and pressure variation remains unclear. This study utilizes molecular dynamics simulations to reveal their relationship by investigating fluid flow in nanopores. Results indicate that under constant nanopore pressure, increasing pressure gradient leads to gradual nanopore expansion. With constant pore width, pressure perpendicular to the flow direction (z and y directions) increases progressively with an increased pressure gradient. Nanopore expansion is attributed to increased pore pressure, resulting from enhanced collision forces and frequencies between fluid atoms and between fluid and wall atoms. This is corroborated by mean square displacement and kinetic energy calculations. In the z direction, increased kinetic energy and pressure primarily stem from enhanced fluid-fluid and fluid-wall collisions. In the y direction, these increases are mainly due to enhanced fluid-fluid collisions. The influence of rough surfaces was also studied. This research provides a theoretical foundation for nanopore pressure calculation when considering fluid flow effects, advancing our understanding of nanoscale fluid dynamics.